The ultimate objective of the research is to develop a sub-minature motor driven axial flow pump that 1) won't cause undue damage to the blood, 2) will be fully implantable allowing the chest to be closed, and 3) will provide cardiac support for up to 96 hours. The purpose of this Phase I effort is to prove the feasibility of using a sub-miniature pump placed directly in the blood stream to pump blood in a chronic nonpulsatile mode as a short term left ventricular assist device. An existing pump design will be modified in part with thrombo-resistant materials. The pump will be tested in three in-vivo tests using living dogs. The tests are primarily intended to detect any blood damage caused by the presence and action of the pump and to reveal any effects the blood might have upon pump operation. Alternate pump materials and coatings will be selected and tested in search of compatibility. The existing pump has fewer parts, is much smaller and much simpler than other cardiac assist and artificial heart devices. The smaller device allows ease of insertion and lends itself to closure of the chest, leading to improved patient comfort and a lower risk of infection.